Conventionally, as this kind of gymnastic floor, the following floors as disclosed by the below-listed Patent Documents 1 and 2 are publicly-known and in practical use.
(Patent Document 1): Japanese Unexamined Laid-open Patent Publication No. 2004-81838
(Patent Document 2): U.S. Pat. No. 4,648,592
These gymnastic floors, typically, have the following structure.
As shown in FIGS. 11 and 12, a plurality of rigid unit floor panels 101, such as rectangular plywood panels, each equipped with a plurality of elastically supporting leg members 102 on its bottom surface, are arranged on a structural body floor surface F of a building in a matrix arrangement and integrally joined with each other to form a collective floor substrate of a predetermined area. On the upper surface of the floor substrate, an elastic layer 103 made of a single or stacked multiple layers 103a and 103b of resin foam are disposed. Furthermore, on the top surface of the elastic layer 103, a fiber mat 104, such as a cut pile carpet, is laid to thereby provide an elastic floor surface for gymnastics that exerts given strong elasticity against a vertical load.